// SPDX-FileCopyrightText: Adam Evyčędo
//
// SPDX-License-Identifier: GPL-3.0-or-later

package xyz.apiote.fruchtfleisch

import java.io.EOFException
import java.io.InputStream
import java.lang.Double.longBitsToDouble
import java.lang.Float.intBitsToFloat

data class IntVar(private val v: Long) {
	fun toLong() = v
}
data class UIntVar(private val v: ULong) {
	fun toULong() = v
}

@Suppress("MemberVisibilityCanBePrivate", "unused", "BooleanMethodIsAlwaysInverted")
class Reader(private val stream: InputStream) {
	fun readUInt(): UIntVar {
		var result: ULong = 0UL
		var i = 0
		var s = 0
		while (true) {
			val b = stream.read()
			if (b < 0) {
				throw EOFException("while reading byte")
			}
			if (b < 0x80) {
				if (i > 9 || (i == 9 && b > 1)) {
					TODO("throw int overflow")
				}
				result = result.or(b.toULong().shl(s))
				break
			}
			result = result.or(b.toULong().and(127u).shl(s))
			i++
			s += 7
		}
		return UIntVar(result)
	}

	fun readInt(): IntVar {
		val unsigned = readUInt().toULong()
		var signed = unsigned.shr(1).toLong()
		if (unsigned.and(1UL) != 0UL) {
			signed = signed.inv()
		}
		return IntVar(signed)
	}

	fun readU8(): UByte {
		val b = stream.read()
		if (b < 0) {
			throw EOFException("while reading byte")
		}
		return b.toUByte()
	}

	fun readU16(): UShort {
		val b1 = readU8()
		val b2 = readU8()
		return (b2.toUInt().shl(8) or b1.toUInt()).toUShort()
	}

	fun readU32(): UInt {
		val b1 = readU8()
		val b2 = readU8()
		val b3 = readU8()
		val b4 = readU8()
		return b4.toUInt().shl(24) or b3.toUInt().shl(16) or b2.toUInt().shl(8) or b1.toUInt()
	}

	fun readU64(): ULong {
		val b1 = readU8()
		val b2 = readU8()
		val b3 = readU8()
		val b4 = readU8()
		val b5 = readU8()
		val b6 = readU8()
		val b7 = readU8()
		val b8 = readU8()
		return b8.toULong().shl(56) or b7.toULong().shl(48) or b6.toULong().shl(40) or b5.toULong().shl(32) or b4.toULong().shl(24) or b3.toULong().shl(16) or b2.toULong().shl(8) or b1.toULong()
	}

	fun readI8(): Byte {
		return readU8().toByte()
	}

	fun readI16(): Short {
		return readU16().toShort()
	}

	fun readI32(): Int {
		return readU32().toInt()
	}

	fun readI64(): Long {
		return readU64().toLong()
	}

	fun readFloat32(): Float {
		return intBitsToFloat(readI32())
	}

	fun readFloat64(): Double {
		return longBitsToDouble(readI64())
	}

	fun readData(n: Int): ByteArray {
		val data = ByteArray(n)
		var left = n
		while (left > 0) {
			val r = stream.read(data, n - left, left)
			if (r == -1) {
				break
			}
			left -= r
		}
		return data
	}

	fun readString(): String {
		val length = readUInt()
		return readData(length.toULong().toInt()).decodeToString()
	}

	fun readBoolean(): Boolean {
		return when (readU8().toUInt()) {
			0u -> false
			1u -> true
			else -> TODO("throw wrong value")
		}
	}
}